Method for preparing a selectively permeable protective structure

ABSTRACT

A method for preparing a selectively permeable protective structure. The selectively permeable structure comprises a membrane having a moisture vapor permeation value of at least 200 g-mil/m 2 /24 h and barrier to liquid water, and a supporting substrate.

This application claims priority to U.S. provisional application61/172,036, filed Apr. 23, 2009 now pending and U.S. provisionalapplication 61/237,789, filed Aug. 28, 2009 now pending; the entiredisclosures of which are incorporated herein by reference.

This invention relates to a method for preparing a selective permeablestructure.

BACKGROUND

Personal protection from exposure to harmful chemical and biologicalagents is often of concern to firefighters, medical practitioners andsimilarly situated personnel. Such protection often includes the use ofapparel that provides a barrier to such agents. Butyl rubber is oftenused in standard protective clothing. However, garments made from butylrubber are bulky and nearly impermeable to air and moisture (I. Lee,Yang and Wilusz;

Polymer Engineering & Science, 1996, 36, 1217) resulting in unbearablelevels of heat inside the garments during use. Other protective apparelincludes textiles coated with polymeric materials to provide a chemicaland/or biological barrier.

Equipment is often wrapped or packaged with film or fabric tarpaulins,hoods or other covers to prevent surface damage during transportationand storage. These covers may be prepared from high barrier (highlymoisture impermeable) films and fabrics (see, e.g.,http://www.heritagepackaging.com/productservices/barrierpackaging/bpbasics/bpbasics.htm).

Many relatively small items are shipped on pallets, that is, platformsthat are easily moved by forklifts or small cranes. Pallets provideconvenience in loading and unloading goods from shipping containers, andin moving smaller amounts of goods over shorter distances, such aswithin warehouses, or to deliver a retail quantity. The small items maybe unpackaged or packaged, for example in bags or boxes, when they areplaced on the pallets.

A loaded pallet preferably has integrity and stability, so that thegoods are not damaged or lost during shipping. To provide the necessaryintegrity and stability, the pallet and its load have been typicallywrapped together in film, for example overlapping layers of polyethylenestretch wrap that may be applied by machine or by hand. See, e.g., USRE38429. Other generally practiced methods of providing integrity andstability to loaded pallets include wrapping the pallet and its load inheat shrinkable film, encasing the loaded pallet in a sheath or “hood”which may be heat shrinkable or stretchable, and containing the goods ina single carton or box. These methods are sometimes referred to,individually or collectively, as “pallet unitizing”.

Using barrier films for wrapping small objects or articles in sealedbags is generally suitable since the object may be dried before beingsealed in the bags and/or drying agents may be included inside thesealed bags. This approach is less suitable for large objects such asvehicles, boats, motors, machinery, industrial goods, pallets orcontainers holding smaller articles, and other bulky equipment becausethe covers are typically not hermetically sealed around the object andthorough drying of the object may not be feasible. This may beespecially problematic during storage or when shipping by ship orrailroad, because the large objects may be exposed to adverse weatherconditions for long periods of time. Atmospheric moisture and/or rainmay enter the space under the cover and be trapped and condense. Withhigh barrier covers, there is no way for water to permeate back outsidethe cover, resulting in a buildup of moisture inside the cover, leadingto the possibility of corrosion.

Large amounts of money are lost each year because of corrosion of, forexample, iron, steel, and other metals. There are many factors affectingcorrosion rate including moisture, oxygen, and salt presence. A commoncorrosion occurs due to electrochemical reactions at high humidityconditions. For example, when iron is exposed to moist air, it reactswith oxygen to form rust (iron oxide). The result of corrosion may bethe formation of metal oxide that flakes off easily, causing extensivepitting thereby causing structural weakness and disintegration of themetal. Corrosion can also affect other properties of metal parts such asreducing conductivity or increasing surface roughness so that movingparts become unable to move freely.

In addition to corrosion of metals, mold growth may occur in thecondensed moisture on the surface of the equipment.

Using a film or cover with a high water vapor transmission rate canprevent condensation of water inside the cover by allowing equilibrationof the trapped moisture back into the surrounding atmosphere. Using sucha film prevents or reduces rust formation and corrosion and reduces theopportunity for mold growth.

Various permeable materials having a wide range of mechanical andtransport properties are known. Depending upon the particularapplication in which the permeable material is to be employed, however,certain combinations of properties are required. For example, in aprotective apparel application, it is desirable that the material maytransport water vapor and block the transport of harmful chemicalsand/or biological agents, and be lightweight and flexible over a broadtemperature range. A need exists for a material that can be a flexible,solid material with membrane characteristics that facilitate thetransport of water vapor, for example, from a wearer ofmembrane-containing apparel to the atmosphere; allow moisture topermeate the garments to the extent necessary to afford comfort to thewearer, thus reducing heat stress; and block entry of certain chemicalcompounds and biological agents.

Many previous permeable membranes are microporous (i.e., permeable dueto the presence of microscopic pores through which vapor can pass).Microporous membranes, which may be laminated on or between nonwoventextiles, have increased permeability, but may not provide adequatebarriers to liquids because of their nonselective permeability. Liquidsunder pressure may be able to penetrate the pores. Most microporousfilms are biaxially oriented, so only a small amount of shrinkage ispossible, and they cannot be shrunk without losing their porosity. Theymay also have low tear strength and their surfaces may be easily fouled,thereby losing permeability.

Various references describe semipermeable materials produced from avariety of polymers that may be useful for protective covers. See e.g.,U.S. Pat. No. 6,579,948. Recently protective fabrics comprising aselectively permeable membrane comprising organic acid-modified ionomercompositions have been disclosed (U.S. Pat. No. 7,514,380). Althoughcompositions disclosed therein provide excellent selective permeability,adhesion to certain textiles may be insufficient to provide a robustprotective structure.

Because no single material has emerged which satisfies all of thetechnical requirements and that presents a cost-effective alternative,it is desirable to provide a selectively permeable membrane or structureor layer that displays a combination of mechanical properties, lowtemperature flexibility, selective transport, ease of processability,and cost-effectiveness, so as to render it suitable for use as aprotective cover for objects that limits corrosion and/or mold growth.

SUMMARY OF THE INVENTION

This invention provides a method for preparing a selectively permeablemultilayer structure or article comprising or consisting essentially of:

1) preparing a first composition comprising, consisting essentially of,or consisting of

(i) one or more ethylene acid copolymers; and

(ii) one or more organic acids; wherein at least 50% of the combinedacidic groups in the acid copolymer and the organic acid are nominallyneutralized to salts with metal ions and at least 50% of the metal ionsare alkali metal ions;

(2) melt blending the first composition with a terpolymer of ethylene,acrylic acid or methacrylic acid, and an alkyl acrylate or alkylmethacrylate;

and optionally with one or more ethylene-containing polymers selectedfrom the group consisting of polyethylene (PE) homopolymers, copolymersof ethylene and an α-olefin, copolymers of ethylene and a diolefin, andethylene copolymers obtained from copolymerization of ethylene with atleast one polar monomer selected from the group consisting of vinylacetate, acrylic ester, methacrylic ester and carbon monoxide, whereinthe ethylene-containing polymer does not comprise a carboxylic acidcomonomer, to provide a second composition in a molten condition;

3) contacting a substrate with the molten second composition to adhere,embed, or impregnate the melted composition to the substrate or adhere,embed, or impregnate the substrate to the molten second composition toprovide a coated substrate;

4) cooling the coated substrate to allow the molten second compositionto cool and solidify.

In the method, the one or more ethylene acid copolymers may comprise anE/W ethylene acid copolymer or ionomer of the acid copolymer wherein Erepresents copolymerized units of ethylene, W is present in about 2 toabout 35 weight % of the copolymer and represents copolymerized units ofat least one C₃ to C₈ α,β-ethylenically unsaturated carboxylic acid; andthe one or more monocarboxylic acids have from 4 to 36 carbon atoms, orsalts thereof.

An embodiment is one in which the second composition comprises, consistsessentially of, or consists of

(a) 30 to 99 weight %, based on the combination of (a), (b) and (c), ofa blended combination of

(1) 70 to 90 weight %, based on the combination of (1) and (2), of oneor more E/W ethylene acid copolymers or ionomers of the acid copolymerswherein E represents copolymerized units of ethylene, X is present inabout 2 to about 35 weight % of the copolymer and representscopolymerized units of at least one C₃ to C₈ α,β-ethylenicallyunsaturated carboxylic acid;

(2) 10 to 30 weight %, based on the combination of (1) and (2), of oneor more organic acids having from 4 to 36 carbon atoms, or saltsthereof; wherein at least 50% of the combined acidic groups in the E/Wcopolymer and the organic acid are nominally neutralized to salts withmetal ions; wherein at least 50% of the metal ions are alkali metalions;

(b) 1 to 30 weight %, based on the combination of (a), (b) and (c), ofE/X/Y ethylene acid terpolymers wherein E represents copolymerized unitsof ethylene, X is present in about 2 to about 35 weight % of thecopolymer and represents copolymerized units of acrylic acid ormethacrylic acid, and Y is present in about 1 to about 35 weight % ofthe copolymer and represents copolymerized units of alkyl acrylate oralkyl methacrylate; and

(c) 0 to 60 weight %, based on the combination of (a), (b) and (c), ofone or more second ethylene-containing polymer selected from the groupconsisting of polyethylene homopolymers, copolymers of ethylene and anα-olefin, copolymers of ethylene and a diolefin, and ethylene copolymersobtained from copolymerization of ethylene with at least one polarmonomer selected from the group consisting of vinyl acetate, acrylicester, methacrylic ester and carbon monoxide, wherein the secondethylene-containing polymer does not comprise a carboxylic acidcomonomer; wherein (a), (b) and (c) total 100 weight %.

Of note is the method wherein the second composition comprising (a), (b)and optionally (c) has greater adhesion to the substrate than acorresponding composition comprising (a) that does not comprise (b), theother components being identical.

The method can be used to prepare a selectively permeable structure thatcan be used as a protective article. Notably, the second composition hasa moisture vapor permeation value (MVPV) of at least 200 g-mil/m²/24 hand high water-entry pressure; and the selectively permeable structurehas a moisture vapor transmission rate (MVTR) of at least 30 g/m²/24 h.The MVPV and MVTR are measured at 37.8° C. and 100% relative humidityaccording to ASTM F-1249.

DETAILED DESCRIPTION OF THE INVENTION

The entire disclosures of all references are incorporated herein byreference and tradenames or trade marks are shown in upper case. Theword(s) following the verb “is” can be a definition of the subject.

“(Meth)acrylic acid” includes methacrylic acid and/or acrylic acid and“(meth)acrylate” includes methacrylate and/or acrylate.

“Selectively permeable” means permeation is allowed only to certainmolecules in a specific state such as vapor or gas and not to othermolecules or in a different state such as liquid or solid. Suchmolecules can be dissolved or dispersed in the matrix of certainmaterials such as a film or sheet of the composition disclosed hereinand thereafter be diffused or migrated through the material.

The selectively permeable composition may have MVPV of at least 200, atleast 800, at least 900, at least 1200, at least 2000, at least 4,000g-mil/m²/24 h, or even higher. MVPV is an indicator of the inherentpermeability of the composition, by measuring moisture permeation of amembrane comprising the composition, which may be a film or sheet thatis normalized to 1 mil thickness.

Selectively permeable protective articles may have MVTR of at least 30,at least 50, at least 100, at least 500, or at least 1000 g/m²/24 h, oreven higher. MVTR measures total moisture vapor transmitted through anarticle across its smallest dimension during a unit time, disregardingthe structure thickness. For a membrane of a given composition and MVPV,MVTR decreases as the thickness increases.

A selectively permeable article provides a combination of mechanicalproperties, low temperature flexibility, selective transport, ease ofprocessability, and cost-effectiveness.

Extrusion coating a selectively permeable composition comprising anorganic acid modified-ionomer composition, as disclosed in U.S. Pat. No.7,514,380, onto substrates such as paper or fabrics has experienced pooradhesion of the composition to the substrate. Previously, inclusion of20 to 30 weight % of ethylene alkyl (meth)acrylate copolymers have beenused to improve adhesion of other selectively permeable compositions(e.g., copolyester amide copolymers [PEBAX®]) to substrates. Whileimproving adhesion, the ethylene alkyl (meth)acrylate copolymers mayhave a negative effect on the moisture breathability of the coating.

Surprisingly, an ethylene acrylic acid alkyl (meth)acrylate terpolymer(e.g., ethylene (meth)acrylic acid n-butyl acrylate terpolymer) can beeffective in promoting the adhesion of organic acid-modified ionomer tofabrics under relatively mild processing conditions. At 10 weight %level (versus a typical modification level of 30 weight % for ethylenealkyl acrylate dipolymers) such a terpolymer demonstrated enhancedfabric adhesion, while adequately retaining the moisture permeability ofthe original organic acid modified ionomer.

The composition can be formed into a monolithic or continuous membranethat functions as a selectively permeable barrier. Monolithic continuousmembranes, in contrast to microporous membranes, have high water-entrypressure and are waterproof and liquidproof. High water-entry pressurerefers to >150 cm (or >250 cm or >500 cm) H₂O hydrostatic head, asdescribed in DIN EN20811:92.

Therefore, monolithic membranes provide barriers to liquids such aswater, while still allowing permeability to water vapor underappropriate conditions. A monolithic barrier is also effective atpreventing exposure to liquids such as water, solvents, oils, corrosivefluids and the like, or particulates or solids, including dust,irritants, mold spores, allergens, pollen, animal dander, hair and thelike.

The selectively permeable membrane may be selective to liquid penetrantsdepending on the size and polarity of the penetrants, i.e., hasselectivity so as to be capable of allowing water to diffuse through ata higher rate than virtually all organic liquids having a molecularweight higher than that of methanol.

The acid copolymers used in the method are preferably “direct” or“random” acid copolymers. Direct or random copolymers are polymerspolymerized by adding all monomers simultaneously, as distinct from agraft copolymer, where another monomer is grafted onto an existingpolymer, often by a subsequent free radical reaction.

In the first step of the method, an organic acid-modified ionomer isprepared from an ethylene acid copolymer that comprises one or more E/Wcopolymers where E represents copolymerized units of ethylene, Wrepresents copolymerized units of at least one C₃-C₈ α,β-ethylenicallyunsaturated carboxylic acid, and W can be from about 3 to 35, 4 to 25,or 5 to 20, weight % of the E/W copolymer and ethylene can make up therest.

Examples of W include acrylic acid or methacrylic acid. Specific acidcopolymers include ethylene/acrylic acid dipolymers andethylene/methacrylic acid dipolymers. An ethylene/methacrylic aciddipolymer of note comprises 19 weight % of copolymerized units ofmethacrylic acid.

Ethylene acid copolymers may be produced by any methods known to oneskilled in the art such as use of “co-solvent technology” disclosed inU.S. Pat. No. 5,028,674.

Ionomers are obtained by neutralization of an acid copolymer.Neutralizing agents including metal cations such as sodium or potassiumions are used to neutralize at least some portion of the acidic groupsin the acid copolymer. Unmodified ionomers are prepared from the acidcopolymers such as those disclosed in U.S. Pat. No. 3,264,272.“Unmodified” refers to ionomers that are not blended with any materialthat has an effect on the properties of the unblended ionomer. The acidcopolymers may be used to prepare unmodified, melt processable ionomersby treatment with a metal compound. The unmodified ionomers may benominally neutralized to any level such as about 15 to about 90% orabout 40 to about 75% of the acid moieties.

The organic acids may be monobasic, having fewer than 36 carbon atoms,or salts thereof. The acids are optionally substituted with from one tothree substituents independently selected from the group consisting ofC₁-C₈ alkyl, OH, and OR¹ in which each R¹ is independently C₁-C₈ alkyl,C₁-C₆ alkoxyalkyl or COR²; and each R² is C₁-C₈ alkyl.

Examples of organic acids include C₄ to C₃₆ (such as C₃₄, C₄₋₂₆, C₆₋₂₂,or C₁₂₋₂₂) acids. At high neutralization such as greater than 80%, up to100%, nominal neutralization (i.e., sufficient metal compound is addedsuch that all acid moieties in the copolymer and organic acid arenominally neutralized), volatility is not an issue and organic acidswith lower carbon content may be used, though it is preferred that theorganic acid (or salt) be non-volatile (not volatilize at temperaturesof melt blending of the agent with the acid copolymer) and non-migratory(not bloom to the surface of the polymer under normal storage conditions(ambient temperatures)). Examples of organic acids include, but are notlimited to, caproic acid, caprylic acid, capric acid, lauric acid,stearic acid, isostearic acid, arachidic acid, behenic acid, erucicacid, oleic acid, and linoleic acid. Organic (fatty) acids includepalmitic acid, stearic acid, oleic acid, erucic acid, behenic acid,isostearic acid, 12-hydroxystearic acid, or combinations of two or morethereof. Saturated organic acids, such as stearic acid, arachidic acid,and behenic acid, may be preferred.

Organic acids may be commercially available as a mixture of namedorganic acid(s) and a number of structurally different organic acids ofvarying lesser amounts. When a composition comprises a named acid, otherunnamed acids may be present at levels conventionally known to bepresent in commercial supplies of the named acid. For example, acommercially available mixture of acids includes 90 weight % of amixture of arachidic acid (C₂₀ acid) and behenic acid (C₂₂ acid) with 6weight % of C₁₈ acids and 4 weight % of other acids.

Salts of any of these organic acids may include the alkali metal salts,such that the metal ions present in the final composition comprise atleast 50% of alkali metal ions, including lithium, sodium, potassiumsalts and/or cesium salts, preferably sodium salts or potassium salts.

The amount of basic metal compound capable of neutralizing acidic groupsmay be provided by adding the stoichiometric amount of the basiccompound calculated to neutralize a target amount of acid moieties inthe acid copolymer and organic acid(s) in the blend (herein referred toas “% nominal neutralization” or “nominally neutralized”). Thus,sufficient basic compound is made available in the blend so that, inaggregate, the indicated level of nominal neutralization could beachieved. Greater than 50%, 60%, 70%, 80% or 90% (or even 100%) of thetotal acidic groups in the E/X/Y copolymers and organic acids may benominally neutralized with metal ions; and the metal ions comprise atleast 50 mole % alkali metal ions, preferably sodium or potassium. Smallamounts of salts of alkaline earth metal and/or transition metal ionsmay be present in addition to the alkali metals.

Metal compounds may include compounds of alkali metals, such as lithium,sodium, potassium, or cesium or combinations of such cations. Examplesinclude sodium, potassium, cesium or any combination of sodium,potassium, and/or cesium, optionally including small amounts of othercations such as other alkali metal ions, transition metal ions oralkaline earth ions. Metal compounds of note include formates, acetates,nitrates, carbonates, hydrogencarbonates, oxides, hydroxides oralkoxides of the ions of alkali metals, especially sodium and potassium,and formates, acetates, nitrates, oxides, hydroxides or alkoxides of theions of alkaline earth metals and transition metals. Of note are sodiumhydroxide, potassium hydroxide, sodium acetate, potassium acetate,sodium carbonate and potassium carbonate.

The ethylene acid copolymers or unmodified ionomers may be mixed withorganic acids or salts thereof and/or metal compounds, by any meansknown to one skilled in the art, to prepare a blended modified ionomercomposition comprising (1) and (2) as described above. It issubstantially melt-processable and may be produced by combining one ormore ethylene acid copolymers, one or more monobasic carboxylic acids orsalts thereof, basic compound(s) to form a mixture; and heating themixture under a condition sufficient to produce the composition. Heatingmay be carried out under a temperature in the range of from about 80 toabout 350, about 100 to about 320, or 120 to 300° C. under a pressurethat accommodates the temperature for a period from about 30 seconds toabout 2 or 3 hours. For example, the composition may be produced bymelt-blending an acid copolymer and/or ionomer thereof with one or moreorganic acids or salts thereof; concurrently or subsequently combining asufficient amount of a basic metal compound capable of neutralization ofthe acid moieties to nominal neutralization levels greater than 50, 60,70, 80, 90%, to near 100%, or to 100%. A salt-and-pepper blend ofcomponents may be heated or the components may be melt-blended in anextruder. For example, a twin-screw extruder may be used to mix andtreat the acid copolymer and the organic acid (or salt) with the metalcompound at the same time. It is desirable that the blending isconducted so that the components are intimately mixed, allowing thebasic metal compound to neutralize the acidic moieties.

Treatment of acid copolymers and organic acids with metal compounds inthis manner (concurrently or subsequently), such as without the use ofan inert diluent, may produce a composition without loss ofprocessability or properties such as toughness and elongation to a levelhigher than that which would result in loss of melt processability andproperties for the ionomer alone.

In a second step, the organic acid-modified ionomer is melt blended withan E/X/Y ethylene acid terpolymer and optionally a secondethylene-containing polymer as defined above.

The ethylene acid terpolymers are preferably direct or random acidcopolymers. The ethylene acid terpolymer component comprises one or moreE/X/Y terpolymers where E represents copolymerized units of ethylene, Xrepresents copolymerized units of at least one C₃-C₈ α,β-ethylenicallyunsaturated carboxylic acid, Y represents copolymerized units of asoftening comonomer (softening means that the polymer is made lesscrystalline).

Examples of X include acrylic acid or methacrylic acid and X can be fromabout 3 to 35, 4 to 25, or 5 to 20, weight % of the E/X/Y copolymer andethylene can make up the rest. Examples of Y include alkyl acrylate,alkyl methacrylate, or combinations thereof wherein the alkyl groupshave from 1 to 8, or 1 to 4, carbon atoms. Notable are E/X/Y copolymerswherein Y is present in at least 1 weight %, or about 2 to about 35weight % of the E/X/Y copolymer. Ethylene can make up the rest of theE/X/Y terpolymer.

Specific terpolymers include ethylene/acrylic acid/n-butyl acrylate,ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylicacid/iso-butyl acrylate, ethylene/methacrylic acid/iso-butylmethacrylate, ethylene/acrylic acid/methyl acrylate,ethylene/methacrylic acid/methyl methacrylate, ethylene/acrylicacid/ethyl acrylate and ethylene/methacrylic acid/ethyl methacrylateterpolymers, or combinations of two or more thereof.

Preferably, the modified ionomer combination of (1) and (2) is preparedand subsequently blended with the E/X/Y terpolymer. Blending the E/X/Yterpolymer with the E/W dipolymer prior to, or simultaneously with,conversion of the E/W dipolymer to the organic acid-modified ionomer mayresult in a composition in which improved adhesion to substrates is notobserved.

Optionally, an additional ethylene-containing polymer may be blendedwith the organic acid-modified ionomer and E/X/Y terpolymer. Blendingwith such polymers may provide better processability, improvedtoughness, strength, flexibility, and/or compatibility of the blend whenadhering to a substrate as described below. The compositions maycomprise 0 to 60 weight %, preferably 0 to 30 weight % of the additionalethylene-containing polymer, such as 0.1 to 60 weight % or 0.1 to 30weight %.

The ethylene-containing polymers may include polyethylene (PE)homopolymers and copolymers. PE homopolymers and copolymers may beprepared by a variety of methods, for example, the well-knownZiegler-Natta catalyst polymerization (e.g., U.S. Pat. No. 4,076,698 andU.S. Pat. No. 3,645,992), metallocene catalyzed polymerization, VERSIPOLcatalyzed polymerization and by free radical polymerization. Thepolymerization may be conducted as solution phase processes, gas phaseprocesses, and the like. Examples of PE polymers may include highdensity PE (HDPE), linear low density PE (LLDPE), low density PE (LDPE),very low or ultralow density PEs (VLDPE or ULDPE), lower density PE madewith metallocene having high flexibility and low crystallinity (mPE).Metallocene technology is described in, for example, U.S. Pat. Nos.5,272,236, 5,278,272, 5,507,475, 5,264,405, and 5,240,894.

The density of PE may range from about 0.865 g/cc to about 0.970 g/cc.Linear PE may incorporate α-olefin comonomers such as butene, hexene oroctene to decrease density to within the density range so described. Forexample, a copolymer may comprise a major portion (by weight) ofethylene that is copolymerized with another α-olefin having 3-20 carbonatoms and up to about 20% by weight of the copolymer. Other α-olefinsare propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene,1-decene, 1-tetradecene, 1-octadecene, or in combinations of two ormore. Of note are metallocene polyethylenes comprising ethylene/octenecopolymers.

The PE copolymer may also be an ethylene propylene elastomer containinga small amount of unsaturated compounds having a double bond. The term“PE” when used herein is used generically to refer to any or all of thepolymers comprising ethylene described above.

Ethylene copolymers having small amounts of a diolefin component such asbutadiene, norbornadiene, hexadiene and isoprene are also generallysuitable. Terpolymers such as ethylene/propylene/diene monomer (EPDM)are also suitable.

The ethylene-containing polymer may include ethylene copolymers obtainedfrom copolymerization of ethylene with at least one polar monomer suchas ethylene/vinyl acetate copolymer (EVA), ethylene/acrylic estercopolymers, ethylene/methacrylic ester copolymers, ethylene/vinylacetate/CO copolymers, ethylene/acrylic ester/CO copolymers, and/ormixtures of any of these.

EVA includes copolymers derived from the copolymerization of ethyleneand vinyl acetate or the copolymerization of ethylene, vinyl acetate,and an additional comonomer. The vinyl acetate comonomer may have 2 to45 or 6 to 30 weight % derived from vinyl acetate. An EVA may have amelt flow rate, measured in accordance with ASTM D-1238, of from 0.1 to60 g/10 or 0.3 to 30 g/10 minutes. A mixture of two or more differentEVAs may be used.

Ethylene/alkyl (meth)acrylate copolymer includes copolymers of ethyleneand one or more C₁₋₈ alkyl (meth)acrylates. Examples of alkyl(meth)acrylates include methyl acrylate, ethyl acrylate and butylacrylate. Examples of the copolymers include ethylene/methyl acrylatecopolymer ethylene/ethyl acrylate copolymer, ethylene/butyl acrylatecopolymer, or combinations of two or more thereof. Alkyl (meth)acrylatemay be incorporated into an ethylene/alkyl (meth)acrylate copolymer at 2to 45, 5 to 45, 10 to 35, or 10 to 28 weight %.

Ethylene/alkyl (meth)acrylate copolymers may be prepared by processeswell known to one skilled in the art using either autoclave or tubularreactors.

See, e.g., U.S. Pat. Nos. 2,897,183, 3,404,134, 5,028,674, 6,500,888,and 6,518,365. Because the methods for making an ethylene/alkyl(meth)acrylate copolymer are well known, the description of which isomitted herein for the interest of brevity. Tubular reactor producedethylene/alkyl (meth)acrylate copolymers are commercially available fromE. I. du Pont de Nemours and Company, Wilmington, Del. (DuPont) such asELVALOY® AC. The ethylene/alkyl (meth)acrylate copolymers may varysignificantly in molecular weight and the selection of the melt index(MI) grade of polymer may be made by balancing the properties of theethylene/alkyl (meth)acrylate copolymer with those of the neutralizedorganic acid and ethylene acid copolymer to provide the desired mix ofpermeability and structural properties needed for a specific variablepermeability construction. A mixture of two or more differentethylene/alkyl (meth)acrylate copolymers may be used. Of note is themethod wherein the second composition has at least one ethylene/alkyl(meth)acrylate copolymer present in from 5 to 30 weight %.

Preferably, the modified ionomer combination of (1) and (2) is preparedand subsequently blended with the E/X/Y terpolymer and the optionalethylene-containing polymer. However, in some embodiments theethylene-containing polymer may be melt blended with the components ofthe organic acid-modified ionomer during its preparation or prior toblending with the E/X/Y terpolymer. That is, blending with theethylene-containing polymer and neutralization of the E/W dipolymer andorganic acid and may be conducted simultaneously in a single processoperation.

In other embodiments the modified ionomer combination of (1) and (2) maybe prepared, melt blended with the ethylene-containing polymer and thenmelt blended with the ethylene acid terpolymer. For example, asalt-and-pepper blend of the organic acid-modified ionomer and theethylene-containing polymer may be heated above their meltingtemperatures and mixed or the components may be melt-blended in anextruder. The resulting composition may be collected, for example aspellets, and subsequently blended with the E/X/Y terpolymer.

In other embodiments the organic acid-modified ionomer may be preparedand melt blended with the ethylene-containing polymer and the ethyleneacid terpolymer at the same time, that is, in a single processoperation. A salt-and-pepper blend of the organic acid-modified ionomer,the ethylene-containing polymer and the ethylene acid terpolymer may beheated above their melting temperatures and mixed or the components maybe melt-blended in an extruder, either after pre-blending a pellet blendor by feeding the components to the extruder in metered amounts.

When blending polymeric resins the higher flow or lower viscosity resintends to flow more readily relative to other lower flow resins. Thismelt rheology effect tends to facilitate the higher flow resin todisperse and distribute more effectively in the blend during the meltblending process and enable more effective distribution at the interfacewith higher melt shear field. Depending on the blending and extrusionconditions, the ethylene-containing polymer and the E/X/Y terpolymercomponents may be concentrated near the surface of the extrudate,providing improved adhesion to the substrate.

The composition may additionally comprise from 0.01 to 15, 0.01 to 10,or 0.01 to 5, weight %, based on the total composition weight, ofadditives including plasticizers, stabilizers including viscositystabilizers and hydrolytic stabilizers, primary and secondaryantioxidants, ultraviolet ray absorbers, anti-static agents, dyes,pigments or other coloring agents, inorganic fillers, fire-retardants,lubricants, reinforcing agents such as glass fiber and flakes, synthetic(for example, aramid) fiber or pulp, foaming or blowing agents,processing aids, slip additives, antiblock agents such as silica ortalc, release agents, tackifying resins, or combinations of two or morethereof. These additives are described in the Kirk Othmer Encyclopediaof Chemical Technology.

The additives may be incorporated into the composition by any knownprocess such as by dry blending, extruding a mixture of the variousconstituents, the conventional masterbatch technique, or the like.

The composition can further comprise a fire retardant such as a chemicaladditive including, but not limited to, phosphorous compounds, antimonyoxides, and halogen compounds, particularly bromine compounds, andothers well known in the art. A loading of such additives can be between20 to 30, or about 25% (of the final air-dried composition or air-driedfilm weight).

The composition may also comprise fillers, fibers, or pulps in addedquantities that may be up to 30 to 40 weight % of the total composition.These materials may provide reinforcement or otherwise modify themechanical properties of the composition, without negatively impactingthe selective permeability of the composition. Fillers include, forexample, inorganic materials such as carbon black, TiO₂, calciumcarbonate (CaCO₃). Fibers, including chopped fibers, include glassfibers, aramid fibers, carbon fibers and the like. Pulps include, forexample aramid micropulps (micropulp has a volume average length fromabout 0.01 to about 100 micro-meters).

The melt blending steps described above provide a selectively permeablecomposition that is subsequently applied to a substrate.

In the method, the composition is applied to a substrate in moltencondition by, for example but not limitation, extrusion coating to asubstrate or lamination of two substrate layers by means of an innerlayer of the composition applied in molten form to adhere the substratestogether. Generally, the substrate and a layer of the third compositionmay be arranged in overlaying or overlapping fashion to provide aprotective structure. When used with a substrate, the selectivelypermeable composition may have a thickness from about 10 to about 250μm.

Extrusion coating the selectively permeable composition onto a substratecan be done as follows: dried granulates or pellets of the blendcomponents fed into a single or double screw extruder, either as asalt-and-pepper blend or from separate feeders and melt blended in theextruder. The components may be melt blended prior to the extrusioncoating operation. The molten polymer composition is passed through aslot die to form a molten polymer curtain. The molten curtain drops ontothe moving substrate to be immediately pressed onto that substrate andcooled by a quench drum or between a chill roll and a nip roll.

Extrusion lamination is similar, except the molten curtain ofselectively permeable composition is dropped between two layers ofsubstrate and then cooled. The result is a structure wherein a layer ofselectively permeable composition is positioned between two layers ofsubstrate. In extrusion lamination, the two substrate layers may be thesame or different for sandwich structures described below.

In some embodiments the polymer composition can be coated directly on asubstrate utilizing fabric impregnation and coating techniques. Forexample, the selectively permeable composition is a coating applieddirectly on the substrate (via extrusion coating, spraying, painting orother appropriate application methods). Such coating can be appliedusing spreading methods known in the art such as with a rubber doctorblade or with a slit extrusion machine.

The composition can be applied to one side or both sides of a textilesubstrate. In the case where the substrate is coated or laminated on oneside, the composition may be applied to the side that is directlyexposed to the environment to provide a liquid-impermeable outersurface. Alternatively, in applications where mechanical wear orabrasion is likely, the composition may be applied to the side of thetextile substrate opposite the side exposed to the mechanical wear toafford protection of the polymeric composition.

In other embodiments the composition can be impregnated in a substrateor the substrate can be impregnated in the polymer.

The selectively permeable composition may be formed at least partiallyin the substrate by impregnating the substrate with the composition byapplying the molten composition to the substrate and then cooling thecomposition while it is in contact with the pores of the substrate.

The composition can be dispersed throughout the substrate such as aloosely woven fabric where the composition fills gaps in the substrateand does not just adhere on the surface of a substrate. The substratecan be impregnated inside the selectively permeable membrane throughlamination or coextrusion process to have the permeable compositions onboth sides of the substrate.

The composition can also be accommodated between two layers of textilesin a sandwich-like manner. Several layer assemblies can also beassembled one above the other. For example, the configuration cancomprise the selectively permeable membrane layer, a substrate layer,another selectively permeable membrane layer, another substrate layer,and so on, depending upon desired applications of the protectivestructure. Other configurations can comprise variations of theaforementioned sandwich configuration, including a plurality ofselectively permeable membrane layers, a plurality of substrate layers,and so forth, including mixtures thereof.

The substrate may be any material providing support, shape, estheticeffect, protection, surface texture, bulk volume, weight, orcombinations of two or more thereof to enhance the functionality andhandability of the structure.

A substrate can be a vehicle to aid in incorporating the selectivelypermeable composition or provide mechanical support for the membrane sothat permeability is not hindered. Preferably a substrate has watervapor diffusion that is greater than the water vapor diffusion of theselectively permeable membrane so that the water vapor diffusioncharacteristics of the structure are essentially provided by theselectively permeable composition. That is, the substrate does notsubstantially affect the passage of water vapor through the layeredstructure, and for example, may have a measured MVTR of at least 1.8, 4,5, or even 10, Kg/m²/24 hours.

Any support or substrate meeting these desired characteristics may beused with the selectively permeable composition. Examples include atextile or porous sheet material. Sheets made from synthetic fiber spunfabrics, such as nonwoven textiles, may be used as a textile substrate.Cloth that is woven, knitted or the like is also suitable as a textilesubstrate. A fabric may comprise flame retardant(s), filler(s), oradditive(s) disclosed above.

For example, a fabric may comprise a 50% nylon-50% cotton blend wovenfabric (also known as NYCO) such as those by Bradford DyeingAssociation, Inc., in Bradford, R.I. A fabric of note is a polyesterwoven fabric from Millikin and Company (Spartanburg, S.C.).

A textile may also include nonwoven textiles prepared frompolypropylene, polyethene, polyesters such as polyethylene terephthalateor mixtures thereof, and other spun bonded polymer fabrics.

While the substrate has been described generally as a textile, thesubstrate can be any other material that is capable of accommodatingthereon one or a plurality of layers or accommodating therein adispersion of the selectively permeable composition.

Cellulosic materials such as paper webs (for example Kraft or ricepaper), materials made from synthetic fiber spun fabrics, microporousfilms, or even perforated films having large percentages of open areassuch as perforated PE films, may be used as materials for thesubstrate(s), for example. These materials may be reinforced withfibers. Microporous films of note may be prepared from polypropylene,polyethylene or combinations thereof. They may be monolayer ormultilayer films (for example, three-layer films comprising an innerlayer of polypropylene between two outer layers of polyethylene).Microporous films are available from Celgard, LLC, Charlotte, N.C. underthe CELGARD tradename.

Suitable polymers for the a microporous film are (1) linear ultrahighmolecular weight polyethylene having an intrinsic viscosity of at least18, preferably 18 to 39, deciliters/gram, (2) linear ultrahigh molecularweight polypropylene having an intrinsic viscosity of at least 6deciliters/gram, and (3) mixtures of (1) and (2).

The microporous film may include a finely divided, particulate,substantially water-insoluble, inorganic filler, for example a siliceousfiller, which is distributed throughout the matrix and which is presentin amount 50 to 90%, particularly 50 to 85%, by weight of the film. Thefiller may be silica, precipitated silica, or silica having an averageultimate particle size of less than 0.1 μm and may occupy 35 to 80% ofthe total volume of microporous film. Because they have a relativelynarrow range of pore sizes, films may be made by extruding a polymericcomposition which contains an inorganic filler and a processing oil,e.g. a paraffinic oil, naphthenic oil or aromatic oil, uniformlydistributed therein; followed by extraction of the processing oil, e.g.with trichloroethylene. Some films are disclosed, for example, in U.S.Pat. Nos. 4,937,115 and 3,351,495 and films are sold by PPG Industriesunder the tradename TESLIN.

Specific examples of porous or perforated films include a porous PE filmhaving a porosity of about 55% and a pore size of about 0.25 microns,available under the tradename CELGARD K878 from Hoechst Celanese Corp; aporous PE film available under the tradename MSX 1137P from 3M Co.; anda filled porous PE film available under the designation Van Leer 10×from Van Leer Corp. TESLIN SP7 is a filled porous PE films containingabout 60% silica, having a thickness of about 0.18 mm (0.007 inch), atear strength measured as described above of about 90 g, a porosity ofabout 65%, an average pore size of about 0.1 micron and a largest poresize of 4 to 10 microns. TESLIN X457 is similar to TESLIN SP7 but ismore porous. TESLIN SP10 is similar to TESLIN SP7 but has a thickness ofabout 0.25 mm (0.010 inch). All three TESLIN films are available fromPPG Industries. A perforated high density polyethylene film, 0.11 mm(4.5 mil) thick, with an open area of about 36%, is available under thetradename DELNET from Applied Extrusion Technologies.

A substrate can be a porous sheet material comprising a fluoropolymer. Asubstrate can be sheet material made with expandedpolytetrafluoroethylene that is available from many companies, includingW. L. Gore & Associates of Wilmington, Del. Other porous substratesinclude porous or microporous polyurethane films, filter materials fromcompanies such as Millipore, nano- or micro-fiber structures, natural orsynthetic fibers, other related supports that add dimensional stability,or combinations of two or more thereof.

The method provides structures comprising the selectively permeablecomposition and a substrate.

The composition can be used in protective garments and structures, suchas drapes, shelters, tents, and other coverings for personnel orobjects, where it functions as a biological and/or chemical barrier. Theprotective structures can also be in the form of, for example,tarpaulins, covers, and the like. The polymer composition can be presentas a layer of material added to the protective garments or structure, oras one component of a fabric incorporated into the protective garment orstructure.

Coated fabrics, used previously as tarpaulins or other covers, may haveat least one wear resistant outer layer that generally needs highflexibility, high resistance to marring from wear, abrasion, scuffing,and scratching, high mechanical strength and toughness. Coatingcompositions preferably exhibit good adhesion to fabrics and othersubstrates such as plastic films and cellulosic materials such as paperor paperboard. They also desirably exhibit good melt processability,good colorability, good printability, and high transparency and/orgloss. Previous coating compositions for these applications includeplasticized or flexible polyvinyl chloride. The composition describedherein provides a superior coating composition to previous coatingmaterials because it is selectively permeable.

The protective structure may further comprise other layers such asadhesive layers, thermal insulation layers, cushioning layers,absorptive layers, reactive layers, and the like.

Insulation layers and cushioning layers may comprise an organicthermoplastic fiber-based material comprising, e.g., polyester,polyethylene or polypropylene. For example, the thermal insulating orcushioning layer is a fiberfill batt comprising polyester. A fiberfillbatt sold as THERMOLITE ACTIVE ORIGINAL by DuPont is suitable.Alternatively, the thermal insulating layer may comprise melt-blownfibers, such as melt-blown polyolefins, sold as THINSULATE, by 3M. Theymay also include other materials such as fiberglass batts.

The mechanical properties and ease of processing of the selectivelypermeable composition, and its ability to transport water vapor andblock liquids, optionally combined with a support substrate renderprotective structures thereof applicable for covering or enclosingarticles during transport and storage. The structure so made is alsoreferred to as selectively permeable membrane or structure. Themechanical properties and ease of processing of the selectivelypermeable structure, and its ability to transport water and blockorganic molecules, combined with a support substrate render protectivestructures thereof applicable for various applications, such as, forexample, chemical and/or biological protective clothing for health careor military applications. Examples include chemical and/or biologicalprotective apparel comprising any of the aforementioned variousembodiments of the selectively permeable protective structure. Abiological barrier is any structure that provides resistance to harmfulor undesirable biological agents such as bacteria, microbes, viruses andthe like that, for example, may be present in blood, sera, and otherbodily fluids or may be present as aerosols.

The protective structure can be used in protective garments such as forhealth care applications including gowns and other apparel for operatingroom, patient visitor, medical, dental, and similar applications. Theapparel can be selected, for example, from the group consisting ofgowns, aprons, shirts, trousers, overcoats, gloves, shoes, boots,overboots, socks, hoods, hats, caps, masks, and eye goggles. Otherhealth care equipment can be selected, for example, from the groupconsisting of screens, drapes, and breathable dressings.

Protective garments may also be used in military, food preparation,transportation, industrial and manufacturing procedures otherapplications that require protection from biological and/or chemicalagents, heat, irritants and the like. The unique properties of theselectively permeable structure are useful for applications includingprotective clothing for “first responders” in chemical threatsituations, or for hazardous materials handling. In addition to apparellisted above for health care applications, protective apparel may alsoinclude helmets and gas masks.

The selectively permeable protective structure may also be suitable forfabrics used in responding to biological and/or chemical spills. It maybe used for fabrics for tents, awnings and other shelters. These usesmay be protective, since they block transmission of the agent from oneplace to another.

Other uses for the selectively permeable structure include coveringobjects during transportation and storage to provide protection fromliquid water while allowing water vapor to permeate out of the enclosedspace, preventing a buildup of moisture inside the enclosed space,thereby reducing the possibility of corrosion, mold growth and otherdeleterious effects resulting from excess moisture. Articles for thisuse include (1) films or sheets of material comprising the selectivelypermeable structure that may be wrapped around or draped over theobject(s) being packaged such as tarpaulins, pallet wrapping films andthe like; (2) bags, pouches, hoods or sheathes comprised completely ofthe selectively permeable structure described herein or which compriseother materials such as other polymeric materials, woven or nonwoventextiles and the like and have windows, patches or areas thereon whichcomprise the selectively permeable structure, including heat shrinkablehoods and pallet stretch hoods; (3) rigid or semi-rigid or flexiblestructures such as tubs, boxes, bins and the like, comprised completelyof the selectively permeable structure or comprised in part of othermaterials having one or more windows of the variably permeablemultilayer structure thereon; (4) lidding material comprised completelyof the selectively permeable structure or comprised in part of othermaterials having one or more windows of the selectively permeablestructure thereon. The lidding material may be used in combination withrigid or semi-rigid or flexible structures such as tubs, boxes, bins andthe like to prepare a package comprising the selectively permeablestructure; (5) patches of the selectively permeable structure overdesigned openings of packages to provide the desired permeability; and(6) packages in which the selectively permeable structure is covered bya removable protective cover that allows a user to expose theselectively permeable structure to the environment at an appropriatetime.

The following Examples are presented to demonstrate and illustrate, butare not meant to unduly limit the scope of, the invention.

Examples

MI, the mass rate of flow of a polymer through a specified capillaryunder controlled conditions of temperature and pressure, was determinedaccording to ASTM 1238 at 190° C. using a 2160 g weight, in g/10minutes.

For samples with high water permeability (>100 g/m²-24 h), the watervapor transmission tests were conducted on a Mocon PERMATRAN-W 101K,following ASTM D6701-01, at 37.8° C. at 100% relative humidity. For theother samples, the transmission tests were conducted on a MoconPERMATRAN-W 700, following ASTM F1249-01. Moisture vapor permeationvalues (MVPV) on film samples are reported in g-mil/m²-24 h while MVTRare reported in g/m²-24 h. The compositions had MVPV of at least 800 (orat least 1200) g-mil/m²/24 h.

Another method for determining material “breathability,” or evaporativeresistance, uses a Guarded Sweating Hotplate Test according to ASTMF1868, ISO 11092.

Moisture Vapor Transmission Rate (MVTR) of Multilayer Structure

This is measured by a method derived from the Inverted Cup method ofMVTR measurement [ASTM E 96 Procedure BW, Standard Test Methods forWater Vapor Transmission of Fabrics (ASTM 1999)]. A vessel with anopening on top is charged with water and the opening is covered firstwith a moisture vapor permeable (liquid impermeable) layer ofexpanded-PTFE film (“ePTFE”), and then with the sample for which theMVTR is to be measured, and finally by woven fabric overlayer [NYCO50:50 nylon/cotton blend, 6.7 oz/yd² (0.23 kg/m²) treated with durablewater repellant finish]. The three layers are sealed in place, invertedfor 30 minutes to condition the layers, weighed to the nearest 0.001 g,and then contacted with a dry stream of nitrogen while inverted. After19 h at 23° C., the sample is reweighed and the MVTR calculated(kg/m²·24 h) by means of the following equation:

MVTR=1/[(1/MVTR_(obs))−(1/MVTR_(mb))]

where MVTR_(obs) is the observed MVTR of the experiment and MVTR_(mb) isthe MVTR of the ePTFE moisture barrier (measured separately). The valuesare the average of results from three replicate samples.

In order to illustrate the moisture permeance associated with a filmlayer involving a selectively permeable composition as described herein,extrusion cast films were prepared from the materials listed below. Theselectively permeable composition was also extrusion coated ontosubstrates to illustrate its adhesion to the substrates.

Thermoplastic compositions are polymeric materials that can flow whenheated under pressure. Melt index (MI) is the mass rate of flow of apolymer through a specified capillary under controlled conditions oftemperature and pressure. Melt indices reported herein are determinedaccording to ASTM 1238 at 190° C. using a 2160 g weight, with values ofMI reported in grams/10 minutes.

Materials Used

EAC-1: an ethylene/methacrylic acid dipolymer with 19 weight % ofmethacrylic acid, having MI of 395 g/10 min.EAC-2: a terpolymer comprising ethylene, n-butyl acrylate (28 weight %)and acrylic acid (6.2 weight %), having MI of 200 g/10 min.EAC-3: a terpolymer of ethylene, n-butyl acrylate (23.5 weight %) andmethacrylic acid (9 weight %), having an MI of 200 g/10 min.EAC-5: a terpolymer of ethylene, n-butyl acrylate (15.5 weight %) andacrylic acid (8.5 weight %), having an MI of 60 g/10 min.EAC-6: a terpolymer of ethylene, n-butyl acrylate (15.5 weight %) andacrylic acid (10.5 weight %), having an MI of 60 g/10 min.ABA: A mixture containing 90 weight % of a mixture of arachidic acid andbehenic acid with 6 weight % C₁₈ acids and 4 weight % other acidscommercially available under the tradename HYSTRENE® 9022 from Chemtura.EMA-1: An ethylene/methyl acrylate copolymer with 24 weight % methylacrylate with MI of 20 g/10 min.EBA-1: An ethylene/butyl acrylate copolymer with 35 weight % butylacrylate, having melt index of 40 g/10 min.EBA-2: An ethylene/butyl acrylate copolymer with 27 weight % butylacrylate, having melt index of 4 g/10 min.Mod-1: a blend of EAC-2 and 5 weight % ABA wherein 93% of the combinedcarboxylic acid groups in the terpolymer and the ABA were neutralized topotassium salts.EMA-2: An ethylene/methyl acrylate copolymer with 20 weight % methylacrylate with MI of 8 g/10 min.Ionomer I-1: a terpolymer comprising ethylene, n-butyl acrylate (23.5weight %) and methacrylic acid (9 weight percent), neutralized to 52%with sodium using sodium hydroxide, with MI of 1.

Employing a Werner & Pfleiderer twin-screw extruder, a mixture of EAC-1and ABA was neutralized to 93-95% with a masterbatch of potassiumhydroxide in EMA-1 to a neutralization level of 93-95% to provideComposition A. The weight ratios of the polymeric materials aresummarized in Table 1. A portion of Composition A was furtherneutralized with neat potassium hydroxide to provide Composition B.

TABLE 1 Parts by weight % Nominal EAC-1 ABA EMA-1 NeutralizationComposition A 73.2 18.4 8.4 93-95 Composition B 73.2 18.4 8.4 106

Composition A was extrusion coated at 0.8 mil thickness ontopolypropylene nonwoven textile (PP NW) and 50-pound Kraft papersubstrate sheets using an Egan extrusion coating machine equipped with amatte-surface chill roll, an Edlon®/Teflon®-covered pressure roll,corona treater and a Cloeren EBR 40-inch die. The substrates were coronatreated at 3 KW/ft². The machine settings included a 6 inches air gapand 80 psi nip roll pressure. Adhesion was tested by T-peel testaccording to ASTM2234-95. The adhesion peel strength between the coatingand the substrate are summarized in Table 2. In the Tables, theabbreviations indicate as follows: “p”=peels, “d”=delaminates,“ft”=fiber tear, “fp”=fiber peel and “t”=tears. These runs show lowadhesion of Composition A to the nonwoven textile under the conditionsindicated.

TABLE 2 Extrusion Adhesion Temp Chill roll peel Substrate (° C.)Feet/min Temp (° C.) strength Comments PP NW 375 235 69  7 g/in p Kraft375 235 69 115 g/in p PP NW 375 400 71  10 g/in p Kraft 375 400 71 203g/in fp PP NW 400 235 73  8 g/in p Kraft 400 235 73 230 g/in fp PP NW400 400 76  9 g/in p Kraft 400 400 76 316 g/in fp, ft

Composition A was blended with 30 weight % of EMA-2 and then extrusioncoated at 375° F. and 0.8 mil thickness onto polypropylene nonwoventextile (PP NW) and 24-pound Kraft paper substrate sheets, using similarconditions as those above. These runs show low adhesion of Composition Amodified with an ethylene/methyl acrylate copolymer to the nonwoventextile under the conditions indicated.

TABLE 3 Extrusion Adhesion Peel Substrate Temp (° C.) Feet/min strength(g/in) Comments PP NW 370 235 10 p Kraft 370 235 178 fp, p PP NW 370 4007 p Kraft 370 400 137 fp, p

Similarly, Composition A was melt blended with the polyethylenes listedand EAC-2 to provide compositions containing 35 weight % of CompositionA, 10 weight % of EAC-2 and 55 weight % of polyethylene; 30 weight % ofComposition A, 15 weight % of EAC-2 and 55 weight % of polyethylene; 30weight % of Composition A, 15 weight % of EAC-2 and 50 weight % ofpolyethylene; 40 weight % of Composition A, 10 weight % of EAC-2 and 50weight % of polyethylene; or 45 weight % of Composition A, 10 weight %of EAC-2 and 45 weight % of polyethylene.

In order to assess adhesion of compositions wherein Composition A or Bwere modified with various polymers, the following tests were performed.Using a Werner & Pfleiderer twin-screw extruder, the Compositions A andB were melt blended with additional materials to provide thecompositions summarized in Table 4. The compositions in Table 4 wereprocessed into 2-mil-thick cast films.

For the film samples, water vapor permeation tests were conducted on aMocon Permatran-W® 101K, following ASTM D6701-01, at 37.8° C. Watervapor permeation values (WVPV) on film samples are reported ing-mil/m²-24 h while moisture vapor transmission rates (MVTR) arereported g/m²-24 h.

TABLE 4 Weight % WVTR Example Composition A Composition B EBA-1 EAC-2Mod-1 I-1 mil-g/M₂-day C1  100 0 0 0 0 0 12721  2 90 0 10 0 0 0 10193  380 0 20 0 0 0 2910  4 70 0 30 0 0 0 1376  5 90 0 5 5 0 0 7934  6 80 0 1010 0 0 6666  7 70 0 15 15 0 0 2657  8 90 0 0 10 0 0 6663  9 80 0 0 20 00 4019 10 70 0 0 30 0 0 1558 C11 0 100 0 0 0 0 13102 12 0 90 0 10 0 08793 13 0 80 0 20 0 0 4445 14 0 70 0 30 0 0 2102 15 0 90 0 0 10 0 860216 0 80 0 0 20 0 5947 17 0 70 0 0 30 0 4685 18 0 90 0 0 0 10 8464 19 080 0 0 0 20 6507 20 0 70 0 0 0 30 4446

The physical properties of some of the films are summarized in Table 5.To assess adhesion of the compositions to a polypropylene nonwoventextile substrate, the films were heat sealed between two layers ofsubstrate at 325° F. at 40 psi for 1.0 sec to provide a 3-layerstructure of PP nonwoven/film/PP nonwoven.

TABLE 5 Tensile modulus, Elmendorf Tear, Tensile strength, Elongation atbreak, psi g/mil psi % Example MD TD ave MD TD ave MD TD ave MD TD aveC1 25400 18300 21850 9.07 20.6 14.84 1600 1100 1350 290 149 220 2 2120017600 19400 10 24.5 17.25 1730 1140 1435 451 321 386 3 19700 18000 1885012.62 22.13 17.38 1550  880 1215 483 247 365 4 15700 Film tear NA 1.774.38 3.08 1300 Film tear NA 435 NA NA 5 20800 20100 20450 16.57 26.3421.46 1570 1330 1450 388 386 387 6 16400 15100 15750 22.39 53.4 37.901760 1220 1490 539 414 476 7 13700 11100 12400 40.51 77 58.76 1600 10501325 534 386 460 8 19600 18900 19250 20.5 21.42 20.96 1790 1370 1580 487376 432 9 16800 14900 15850 54.05 73.89 63.97 1820 1630 1725 542 518 53010  13200 14400 13800 95.65 154.83 125.24 1790 1452 1621 560 507 534

The adhesion was tested by the T-peel test and reported in Table 6.

TABLE 6 T-peel Strength lbf/in gm/in Standard Standard Example Averagedeviation Average deviation C1 1.267 0.691 652 314 2 1.544 0.708 799 3213 0.823 0.432 427 196 4 1.229 0.423 633 192 5 1.436 0.758 708 344 61.812 0.662 928 301 7 1.528 0.579 787 263 8 2.048 0.573 1023 260 9 1.5340.37 756 168 10 1.433 0.394 725 179 C11 1.12 0.235 508 107 12 1.835 0.27832 122 13 1.789 0.057 811 26 14 1.283 0.071 582 32 15 0.769 0.173 34978 16 0.996 0.456 452 207 17 1.29 0.553 585 251 18 1.085 0.284 492 12919 0.889 0.317 403 144 20 1.003 0.31 455 141

Compositions modified with EAC-2, an ethylene/acrylic acid/n-butylacrylate terpolymer, showed better adhesion to PP nonwoven in thesetests compared to unmodified compositions or compositions modified withethylene/alkyl acrylate dipolymers. Compositions in which theethylene/acrylic acid/n-butyl acrylate terpolymer was in the form of anionomer prior to blending did not exhibit improved adhesion (Examples15-20).

Compositions were prepared as summarized in Table 7 and were extrusioncoated onto polypropylene nonwoven textile (PP NW),polyethylene/polyethylene terephthalate nonwoven textile (PE/PET NW) and50-pound Kraft paper sheets at around 200 feet/minute, using an similarconditions as those described above.

TABLE 7 Example Composition A EBA-2 EMA-1 EAC-2 21 70 30 0 0 22 70 0 300 23 90 0 0 10

The extrusion-coating runs are summarized in Table 8.

TABLE 8 Extrusion Corona Thickness Temperature Treatment Chill rollExample Composition (mil) Substrate (° C.) (Kw/ft²) (° C.) 24 Example 210.8 PP NW 400 3 74 25 Example 21 0.8 Kraft 400 3 74 26 Example 21 1.0 PPNW 420 6 80 27 Example 21 1.0 Kraft 420 6 80 28 Example 21 1.0 PE/PET NW420 6 86 29 Example 21 1.0 Kraft 420 6 86 30 Example 22 1.0 PP NW 420 695 31 Example 22 1.0 Kraft 420 6 95 32 Example 23 1.0 PP NW 420 6 77 33Example 23 1.0 Kraft 420 6 77 34 Example 23 1.0 PE/PET NW 415 4 101 35Example 23 1.0 PE/PET NW 415 4 101 36 Example 23 1.0 PP NW 450 4 111 37Example 23 1.0 Kraft 450 4 111

For the runs in which the substrate was a polypropylene nonwoven, WVTRwas measured on the coating after peeling it from the substrate. For theruns in which the substrate was Kraft paper or PE/PET nonwoven, WVTR wasmeasured on the entire 2-layer structure.

TABLE 9 Adhesion peel Example strength (g/inch) Comments WVTR¹ 24 0.1 p1938 25 62 p 1063 26 0.3 p 2479 27 13 p 856 28 0.5 p NA 29 124 p, fp 62730 29 p, t 1889 31 79 p, fp 1175 32 0.7 p 3760 33 208 fp 1140 34 473 (p,d, fp, t)² 3774 35 633 (p, fp)³ 36 17 p 3301 37 78 p, d 1652 ¹Ing/[m²-day]. ²Inside of roll. ³Outside of roll.

Composition A modified with 10 wt % EAC-2, an ethylene acrylic acidn-butyl acrylate terpolymer, showed good adhesion to Kraft paper andexcellent adhesion to PE/PET NW. These results are superior to thoseobtained when Composition A was modified with 30 weight % EBA-1, anethylene/n-butyl acrylate dipolymer. The composition containing EAC-2also had higher WVTR, showing it retained more moisture permeabilityfrom Composition A.

1. A method for preparing a selectively permeable multilayer structureor article comprising: (1) preparing a first composition comprising (i)one or more ethylene acid copolymers; and (ii) one or more organicacids; wherein at least 50% of the combined acidic groups in the acidcopolymer and the organic acid are nominally neutralized to salts withmetal ions and at least 50% of the metal ions are alkali metal ions; (2)melt blending the first composition with a terpolymer of ethylene,acrylic acid or methacrylic acid, and an alkyl acrylate or alkylmethacrylate; and optionally with one or more ethylene-containingpolymers selected from the group consisting of polyethylene (PE)homopolymers, copolymers of ethylene and an α-olefin, copolymers ofethylene and a diolefin, and ethylene copolymers obtained fromcopolymerization of ethylene with at least one polar monomer selectedfrom the group consisting of vinyl acetate, acrylic ester, methacrylicester and carbon monoxide, wherein the ethylene-containing polymerwherein the ethylene-containing polymer does not comprise a carboxylicacid comonomer, to provide a second composition in a molten condition;(3) contacting a substrate with the molten second composition to adhere,embed, or impregnate the melted composition to the substrate or adhere,embed, or impregnate the substrate to the molten second composition toprovide a coated substrate; (4) cooling the coated substrate to allowthe molten second composition to cool and solidify.
 2. The method ofclaim 1 wherein the substrate comprises textile or porous sheetmaterial.
 3. The method of claim 2 wherein the substrate is one or moreporous films, flash spun non-woven fabrics, woven fabrics of syntheticfibers, natural fibers or combinations thereof, scrims, or filtermaterials.
 4. The method of claim 3 wherein the substrate is a wovenfabric of synthetic fibers, natural fibers or combinations thereof. 5.The method of claim 1 wherein at least 50% of the metal ions are sodiumions.
 6. The method of claim 1 wherein at least 50% of the metal ionsare potassium ions.
 7. The method of claim 1 wherein theethylene-containing polymer is selected from the group consisting ofethylene copolymers obtained from copolymerization of ethylene with atleast one polar monomer selected from the group consisting of vinylacetate, acrylic ester, methacrylic ester and carbon monoxide.
 8. Themethod of claim 7 wherein the ethylene-containing polymer is anethylene/alkyl acrylate or ethylene/alkyl methacrylate copolymer.
 9. Themethod of claim 1 wherein the second composition comprises (a) 30 to 99weight %, based on the combination of (a), (b) and (c), of a blendedcombination of (1) 70 to 90 weight %, based on the combination of (1)and (2), of one or more E/W ethylene acid copolymers or ionomers of theacid copolymers wherein E represents copolymerized units of ethylene, Xis present in about 2 to about 35 weight % of the copolymer andrepresents copolymerized units of at least one C₃ to C₈α,β-ethylenically unsaturated carboxylic acid; (2) 10 to 30 weight %,based on the combination of (1) and (2), of one or more organic acidshaving from 4 to 36 carbon atoms, or salts thereof; wherein at least 50%of the combined acidic groups in the E/W copolymer and the organic acidare nominally neutralized to salts with metal ions; wherein at least 50%of the metal ions are alkali metal ions; (b) 1 to 30 weight %, based onthe combination of (a), (b) and (c), of E/X/Y ethylene acid terpolymerswherein E represents copolymerized units of ethylene, X is present inabout 2 to about 35 weight % of the copolymer and representscopolymerized units of acrylic acid or methacrylic acid, and Y ispresent in about 1 to about 35 weight % of the copolymer and representscopolymerized units of alkyl acrylate or alkyl methacrylate; and (c) 0to 60 weight %, based on the combination of (a), (b) and (c), of one ormore second ethylene-containing polymer selected from the groupconsisting of polyethylene homopolymers, copolymers of ethylene and anα-olefin, copolymers of ethylene and a diolefin, and ethylene copolymersobtained from copolymerization of ethylene with at least one polarmonomer selected from the group consisting of vinyl acetate, acrylicester, methacrylic ester and carbon monoxide, wherein the secondethylene-containing polymer does not comprise a carboxylic acidcomonomer; wherein (a), (b) and (c) total 100 weight %.
 10. The methodof claim 9 wherein the ethylene-containing polymer is selected from thegroup consisting of ethylene copolymers obtained from copolymerizationof ethylene with at least one polar monomer selected from the groupconsisting of vinyl acetate, acrylic ester, methacrylic ester and carbonmonoxide.
 11. The method of claim 10 wherein the ethylene-containingpolymer is an ethylene/alkyl acrylate or ethylene/alkyl methacrylatecopolymer.
 12. The method of claim 7 wherein the second compositioncomprising (a), (b) and optionally (c) has greater adhesion to thesubstrate than a corresponding composition comprising (a) that does notcomprise (b), the other components being identical.
 13. The method ofclaim 1 wherein the second composition has a moisture vapor permeationvalue of at least 200 g-mil/m²/24 h measured at 37.8° C. and 100%relative humidity according to ASTM F-1249 and high water-entrypressure.
 14. The method of claim 1 wherein the selectively permeablestructure has a moisture vapor transmission rate of at least 50 g/m²/24h measured at 37.8° C. and 100% relative humidity according to ASTMF-1249.